Curable resin composition

ABSTRACT

A curable resin composition, which is a solid resin at ordinary temperatures obtained by reacting an epoxy resin with a (meth)acrylic anhydride, contains an unsaturated resin having a (meth)acryloyl group (A) which has a double bond equivalent weight of 200 to 500, an ester number of 100 to 300, and a hydroxyl number of no more than 130, an ethylenically unsaturated monomer (B), and a radical polymerization initiator (C).

TECHNICAL FIELD

The present invention relates to a curable resin composition used in amolding material, and a curable resin composition used in the productionof a fuel cell separator. More specifically, the present inventionrelates to a curable resin composition that exhibits excellentflowability during molding, a superior external appearance for themolded product, and excellent levels of hot water resistance and waterabsorption resistance, as well as a fuel cell separator that uses such acomposition.

Priority is claimed on Japanese Patent Application No. 2003-125092,filed Apr. 30, 2003, the content of which is incorporated herein byreference.

BACKGROUND ART

Many different unsaturated resins can be used in radical-curing moldingmaterials, and examples include unsaturated polyester resins, epoxy(meth)acrylate resins (also referred to as vinyl ester resins), urethane(meth)acrylate resins, allyl ester resins, and (meth)acrylate esteroligomers. Depending on the intended application, a variety of differentproperties may be required of these unsaturated resins. In the case ofmolding materials used in bathtubs, boats or ships, vehicles,engineering and construction, and electronic components and the like,exposure to particularly severe environments can be expected, meaning ahigh level of performance is required. In order to achieve a moldedproduct with excellent physical properties, water resistance, andcorrosion resistance, epoxy (meth)acrylate resins can be used favorablyfor the applications described above.

Because an epoxy (meth)acrylate resin generally contains a large numberof intramolecular hydroxyl groups generated by the reaction between anepoxy resin and (meth)acrylic acid, a molded product produced by curingsuch a resin typically exhibits a high coefficient of water absorption,and as a result, the water resistance and heat resistance tend todeteriorate with use. A molding material in which a polyisocyanatecompound and a hydroxy compound are added, in specific proportions, toan epoxy (meth)acrylate resin is known to improve on this problem (seeJapanese Patent (Granted) Publication No. 2,908,477).

Known methods of improving the hydrophilicity of the epoxy(meth)acrylate resins described above include the use of a photocurableresin composition for a coating material, which contains a liquidreaction product mixture obtained by reacting an epoxy resin, a(meth)acrylic acid anhydride, and (meth)acrylic acid, and also containsa photopolymerizable monomer and a photopolymerization initiator (seeJapanese Examined Patent Application, Second Publication No. Sho55-12043).

In addition, an example of a known vinyl ester resin (epoxy acrylateresin) that uses a similar technique is a liquid epoxy (meth)acrylateresin with a double bond equivalent weight of 170 to 200 for use as acoating material or an adhesive, produced by reacting an epoxy resinwith a (meth)acrylic anhydride (quantity used: 0.9 to 1.0 mols per 1.0mols of epoxy groups) (see U.S. Pat. No. 6,515,166).

Furthermore, curable resin compositions containing a resin such as avinyl ester resin or unsaturated polyester resin, together with acarbon-based filler and a polyisocyanate have already been proposed asseparators for fuel cells (see U.S. Pat. No. 6,251,308).

An unsaturated resin such as an epoxy (meth)acrylate resin or vinylester resin, obtained by reacting a (meth)acrylic anhydride with anepoxy resin, which is able to satisfy, to a high level, all of theaforementioned performance requirements such as handling properties,moldability that enables the filling of molding dies with complexshapes, and favorable molded product characteristics such as mechanicalstrength, corrosion resistance, and long term durability such asresistance to hot water, is as yet unknown. In addition, the use of anunsaturated resin for producing a fuel cell separator molded productthat combines excellent conductivity and gas impermeability withexcellent durability such as corrosion resistance, has also not yet beenproposed.

An object of the present invention is to provide a curable resincomposition for a molding material, which enables the production of amolded product such as the various electrical or electronic memberswhich retains the favorable strength characteristics of an unsaturatedresin in which (meth)acryloyl groups have been introduced into an epoxyresin (hereafter referred to as an epoxy (meth)acrylate resin), suffersno moldability problems such as the separation between the resincomposition and any fillers during molding, or the occurrence of voidsor warping, exhibits excellent filling characteristics for molding dies,exhibits excellent flowability and molded product external appearanceduring molding of the molded product, and also exhibits superiorresistance to water absorption and superior hot water resistance, aswell as to provide a fuel cell separator that uses such a curable resincomposition, and exhibits excellent moldability, dimensional precision,conductivity, heat resistance, mechanical strength, and durability suchas hot water resistance.

DISCLOSURE OF INVENTION

As a result of intensive research aimed at achieving the above object,the inventors of the present invention discovered that by using acurable resin composition obtained by reacting an epoxy resin and a(meth)acrylic anhydride as a molding material, wherein the compositioncontains an unsaturated resin having a (meth)acryloyl group (A), whichhas a specific hydroxyl number, ester number, and double bond equivalentweight, an ethylenically unsaturated monomer (B), and a radicalpolymerization initiator (C), a molded product with excellentflowability during molding, superior molded product external appearance,and excellent hot water resistance and heat resistance could beobtained, and they were thus able to complete the present invention.

In other words, a curable resin composition of the present invention isa resin that is solid at ordinary temperatures, is obtained by reactingan epoxy resin with a (meth)acrylic anhydride, and contains anunsaturated resin having a (meth)acryloyl group (A) which has a doublebond equivalent weight of 200 to 500, an ester number of 100 to 300, anda hydroxyl number of no more than 130, an ethylenically unsaturatedmonomer (B), and a radical polymerization initiator (C).

Furthermore, the present invention also provides a curable resincomposition used for molding a fuel cell separator that includes aconductive carbon material and a polyisocyanate compound.

When used as a molding material, a curable resin composition of thepresent invention exhibits excellent flowability during molding andexcellent handling properties, suffers no moldability problems duringmolding such as the occurrence of filling inconsistencies, voids,warping, or cracking, and enables the provision of a molded product withexcellent transferability from the molding die, and superior dimensionalprecision.

Furthermore, a molded product obtained by curing a curable resincomposition according to the present invention exhibits excellentexternal appearance, and excellent levels of water absorptionresistance, hot water resistance, and mechanical strength, as well asparticularly superior durability such as water resistance. Accordingly,a molded product obtained by curing a curable resin composition of thepresent invention is extremely useful, not only for household equipmentmembers, but also for electronic and electrical members, vehiclemembers, and fuel cell separators used under severe conditions. By usinga curable resin composition of the present invention, industrial memberssuch as fuel cell separators and the like with excellent properties canbe produced economically and stably, using a simple process.

In addition, by using a fuel cell separator of the present invention, afuel cell having high performance and high durability can be provided atlow cost.

BEST MODE FOR CARRYING OUT THE INVENTION

An unsaturated resin having a (meth)acryloyl group (A) that is used inthe present invention is a resin that is solid at ordinary temperatures,which is obtained by reacting an epoxy resin with a (meth)acrylicanhydride, and has a double bond equivalent weight of 200 to 500, anester number of 100 to 300, and a hydroxyl number of no more than 130.

The unsaturated resin (A) comprises a plurality of hydroxyl groups and(meth)acryloyl groups within each molecule arising from ring-openingaddition reactions of epoxy groups. The total number of hydroxyl groupsand (meth)acryloyl groups is preferably at least 4. The number of(meth)acryloyl groups is preferably 3 or greater.

The number average molecular weight of the unsaturated resin (A) istypically within a range from 900 to 10,000, and preferably from 900 to5,000, and even more preferably from 1,000 to 3,000. Provided the numberaverage molecular weight falls within the range from 900 to 10,000,favorable levels of strength, water resistance, and handling areobtained. This number average molecular weight refers to apolystyrene-equivalent value determined by GPC measurement.

The hydroxyl number of the unsaturated resin (A) must be no more than130, and is preferably from 20 to 130, and even more preferably from 30to 100. By adjusting the hydroxyl number to no more than 130, afavorable hot water resistance, and favorable levels of handling,flowability during molding, and molded product external appearance canbe obtained on production of a molded product. Furthermore, by settingthe hydroxyl number to a value from 20 to 130, a viscosity suitable formolding can be obtained via a chain elongation reaction by using athickener (E) such as a polyisocyanate, thus enabling the production ofa high quality molded product with minimal defects such as voidsoccurring during the molding process.

This hydroxyl number describes the number of milligrams of potassiumhydroxide (mgKOH/g) required to neutralize the acetic acid produced whena 1 g resin sample is reacted with an acetylation agent at a prescribedtemperature and for a prescribed time, in accordance with the methodprescribed in JIS K-0070.

One example of a method for controlling the hydroxyl number of theunsaturated resin (A) within a range from 20 to 130 involves calculatingthe theoretical hydroxyl number for the case where 1 mol of(meth)acrylic acid reacts with 1 mol of epoxy groups within the epoxyresin being used, and then using this number as a standard, calculatingthe quantity of (meth)acrylic anhydride that should be used to achievethe targeted hydroxyl number. Based on this result, the actual molarratio of the reactants can be determined. In those cases where the epoxyresin itself has hydroxyl groups, this quantity can be added during thecalculation to enable the required quantity of (meth)acrylic anhydrideto be determined.

Furthermore, a polyisocyanate that exhibits reactivity relative to thehydroxyl groups within the unsaturated resin (A) may also be used, andthe hydroxyl number adjusted to a value within the above range by addingthe polyisocyanate after the ring-opening addition reaction.

In order to lower the coefficient of water absorption for the curedproduct, the ester number of the unsaturated resin (A) must be within arange from 100 to 300, and is preferably from 100 to 280. If the esternumber exceeds 300, then obtaining a balance between favorable hot waterresistance, and favorable strength properties and curability becomesdifficult. If the ester number is lower than 100, then the reactivityfalls, making curing much slower, and making the composition unsuitablefor use as a molding material.

The ester number describes the number produced by subtracting the acidnumber from the number of milligrams of potassium hydroxide required(the saponification number) when a 1 g resin sample is subjected to asaponification reaction using potassium hydroxide at a prescribedtemperature and for a prescribed time, in accordance with the methodprescribed in JIS K-0070.

In addition, in the unsaturated resin (A) described above, the sum ofthe aforementioned hydroxyl number and the ester number is preferablywithin a range from 120 to 320, and even more preferably from 150 to320. If this sum exceeds 320, then the hot water resistance tends todeteriorate unfavorably over time, whereas if the sum is lower than 120,then the reactivity falls, and the curability when used as a moldingmaterial is slow, making the resin undesirable from a handlingviewpoint.

The double bond equivalent weight of the above unsaturated resin (A)must fall within a range from 200 to 500, and is preferably from 210 to400. If the double bond equivalent weight falls outside of this range,then curability problems arise when the resin is used as a moldingmaterial, and the hot water resistance deteriorates. This double bondequivalent weight is the molecular weight of the unsaturated resin per 1mol of double bonds, and is calculated by dividing the weight of theunsaturated resin by the number of mols of unsaturated groupsincorporated within a unit of weight of the unsaturated resin. Theunsaturated groups within the unsaturated resin (A) refers to the(meth)acryloyl groups, and the number of mols of (meth)acryloyl groupswithin the resin can be measured by NMR analysis of the unsaturatedresin (A).

In the unsaturated resin (A), particular emphasis must be placed on theselection of a specific epoxy resin, and the balance between thehydroxyl number and the ester number within the unsaturated resin (A).In addition, by ensuring that, as an indicator of the reactivity of theunsaturated resin (A), the double bond equivalent weight falls withinthe above range, a favorable balance can be achieved between propertiessuch as flowability during molding, external appearance of the moldedproduct, and hot water resistance (strength retention, resistance toweight reduction) in those cases where the resin is used as a moldingmaterial. If the double bond equivalent weight is lower than 200, then amolding material and molded product with excellent hot water resistancecannot be provided by increasing the ester number of the unsaturatedresin (A) in the manner described above.

Epoxy resins that can be used as the raw material for the unsaturatedresin (A) preferably have an epoxy equivalent weight of at least 200,and preferably from 220 to 800, and even more preferably from 220 to500. Resins with epoxy equivalent weights outside this range tend to beinferior in terms of hot water resistance, flowability during molding,or the external appearance of the molded product. This epoxy equivalentweight must be at least 200 in order to enable the unsaturated resin (A)to be adjusted to a specific hydroxyl number and a specific esternumber. Furthermore, in those cases where two or more epoxy resins arecombined as raw materials, the sum of the values generated bymultiplying the blend ratio by the epoxy equivalent weight for each ofthe resins is used as the epoxy equivalent value for the mixed epoxyresin, and this value is preferably 200 or greater.

The above epoxy resin preferably includes an aromatic ring-basedstructure and/or an aliphatic ring-based structure, and suitable resinsinclude glycidyl ethers of multinuclear phenols such as bisphenol Aepoxy resins, biphenol epoxy resins, phenol novolac epoxy resins, cresolnovolac epoxy resins, and brominated epoxy resins, glycidyl ethers ofpolyols such as diglycidyl ethers of alkylene oxide adducts of bisphenolA and diglycidyl ethers of hydrogenated bisphenol A, glycidyl esterssuch as diglycidyl hexahydrophthalate, glycidyl amines such astetraglycidyldiaminodiphenylmethane, as well as bisphenol fluorene epoxyresins and biscresol fluorene epoxy resins. These epoxy resins can beused either alone, or in combinations of two or more different resins.

Of these, the use of novolac epoxy resins is preferred in terms of hotwater resistance and water resistance. Moreover, the use ofdicyclopentadiene-based novolac epoxy resins and biphenyl-based novolacepoxy resins is particularly desirable.

Examples of dicyclopentadiene-based novolac epoxy resins include resinsobtained by reacting dicyclopentadiene and a phenol in the presence ofan acid catalyst, and then stirring the reaction product with activatedwhite clay within an organic solvent (see Japanese Unexamined PatentApplication, First Publication No. Hei 7-252349). Furthermore, examplesof biphenyl-based novolac epoxy resins include the resins obtained byglycidyl etherification of the phenolic hydroxyl groups of a4,4′-biphenyldiylmethylene-phenol resin (see Japanese Unexamined PatentApplication, First Publication No. 2001-64340).

The epoxy resin preferably contains from 30 to 90% by mass, and evenmore preferably from 50 to 80% by mass, of aromatic ring-basedstructural units and/or aliphatic ring-based structural units within themolecule. By using an epoxy resin that contains from 30 to 90% by massof aromatic ring-based structural units and/or aliphatic ring-basedstructural units, the molded product produced from the thus obtainedmolding material exhibits low water absorption, and high levels ofstrength and durability.

Furthermore, in terms of the curability and hot water resistance of theobtained unsaturated resin (A), the number of epoxy groups within eachmolecule of the epoxy resin must be an average of 2.0 groups or greater.In order to further improve the hot water resistance, an average valueof 2.5 groups or more is preferred, and the use of epoxy resins with anaverage of 3 to 5 epoxy groups is particularly desirable.

The (meth)acrylic anhydride used as a raw material for the unsaturatedresin (A) can also use a mixture of (meth)acrylic anhydride and(meth)acrylic acid.

In such cases, the relative proportions of the (meth)acrylic anhydrideand the (meth)acrylic acid, although varying depending on the targethydroxyl number for the unsaturated resin (A), are preferably set sothat the molar ratio between the (meth)acrylic anhydride and the(meth)acrylic acid is within a range from 100/0 to 10/90. Ratios from100/0 to 50/50 are even more desirable. The (meth)acrylic anhydride and(meth)acrylic acid can use commercially available products that havebeen produced industrially. The purity of the (meth)acrylic anhydride ispreferably 95% by mass or higher. Although dependent on the method ofproduction, in those cases where the (meth)acrylic anhydride containsonly (meth)acrylic acid as an impurity, the actual blend ratio of the(meth)acrylic anhydride and (meth)acrylic acid can be controlled so asto obtain the desired unsaturated resin (A).

An example of the reaction method and reaction conditions for producingthe unsaturated resin (A) involves charging a reaction vessel with theaforementioned epoxy resin, raising the temperature to approximately 90°C., and then conducting a reaction under a mixed stream of nitrogen anddry air, with constant stirring, by adding (meth)acrylic anhydridedropwise while paying particular attention to the level of exotherm.Once the heat generation has subsided, the reaction is continued,preferably with the temperature maintained at 90 to 120° C., until thetargeted acid number is obtained, thereby yielding the unsaturated resin(A). If required, reduced pressure treatment may be used in the latterstages of the reaction to remove any excess (meth)acrylic acid and thelike. The reaction method for those cases where a combination of(meth)acrylic anhydride and (meth)acrylic acid is used may involveeither a batch reaction or a segmented reaction. From the viewpoint ofthe ease with which the reaction can be scaled up to industrialproduction a segmented reaction is preferred, and a particularlydesirable method involves charging a reaction vessel with theaforementioned epoxy resin and (meth)acrylic acid, raising thetemperature to approximately 90° C., reacting the (meth)acrylic acidfirst under a mixed stream of nitrogen and dry air, with constantstirring, until an acid number of 0 to 10 is obtained, and subsequentlyadding the (meth)acrylic anhydride dropwise to continue the reaction.The target acid number in this case is from 1 to 10. The end point ofthe resin production is usually set at an acid number of no more than10, and preferably 5 or less.

In the above reaction, a catalyst that accelerates the reaction ispreferably added in a quantity equivalent to 0.1 to 2.0% by massrelative to the combined weight of the epoxy resin and the (meth)acrylicanhydride [which may include (meth)acrylic acid]. Examples of suitablecatalysts include tertiary amine compound such as triethylamine andbenzylamine, organic phosphorus-based compounds such astriphenylphosphine, and quaternary ammonium salts such asbenzyltrimethylammonium chloride. In addition, in order to preventabnormal reactions including gelling, the reaction is preferablyconducted with air being blown through the system. The addition of 0.01to 1.0% by mass of a polymerization inhibitor is also desirable.Examples of suitable polymerization inhibitors include quinones such ashydroquinone and t-butylhydroquinone, and if necessary, other compoundssuch as phenothiazine or the various antioxidants may also be added.

The unsaturated resin (A) preferably contains from 20 to 80% by mass,and even more preferably from 30 to 60% by mass, of aromatic ring-basedstructural units and/or aliphatic ring-based structural units. If thisproportion falls outside this range, then achieving a balance betweencurability, strength, and hot water resistance and the like becomesimpossible.

There are no particular restrictions on the ethylenically unsaturatedmonomer (B), provided it is a monomer that is capable ofcopolymerization with the unsaturated resin (A).

Because the unsaturated resin (A) is either a viscous syrup with nofluidity or a completely solidified solid at ordinary temperatures (25°C.), the ethylenically unsaturated monomer (B) functions as both adiluent and reaction component for the unsaturated resin (A). Theviscosity of the unsaturated resin (A) can be measured when dissolved inthe ethylenically unsaturated monomer (B), and that viscosity ispreferably within a range from 500 to 15,000 mPa·s (at 25° C., in amixed solution containing 80% by mass of the unsaturated resin (A) and20% by mass of a styrene monomer);

By diluting the unsaturated resin (A) using this ethylenicallyunsaturated monomer (B), the handling and moldability properties areimproved during production of a molding material, and the heatresistance and water resistance of the resulting molded product can alsobe improved.

Examples of the ethylenically unsaturated monomer (B) include aromaticvinyl monomers, (meth)acrylates, diallylphthalate esters, vinylcarboxylates, vinyl ethers, and maleimide compounds. Of these, in thecase of molded products such as fuel cell separators that require lowwater absorption and superior heat resistance, aromatic vinyl monomersare preferred.

Specific examples of suitable aromatic vinyl monomers include styrene,t-butylstyrene, vinylnaphthalene, vinylbiphenyl, pentafluorostyrene,vinylpyrene, vinylthiophene, and vinylcarbazole. In order to furtherimprove the water resistance and heat resistance, a divinyl monomer suchas divinylbenzene, divinylnaphthalene, or divinylbiphenyl is preferablycombined with the above aromatic vinyl monomer. These aromatic vinylmonomers typically have an ester number of 0. Furthermore, othermonomers can also be added for the purpose of improving various otherperformance factors, provided their addition does not impair themoldability, water absorption or heat resistance properties.

Specific examples of suitable (meth)acrylate esters includemonofunctional monomers such as dicyclopentenyl methacrylate,dicyclopentenyloxyethyl methacrylate, dicyclopentanyl methacrylate,isobornyl methacrylate, phenoxyethyl methacrylate, and adamantanemethacrylate, as well as bifunctional monomers such as 1,9-nonanedioldimethacrylate, 1,10-dodecanediol dimethacrylate, cyclohexanedimethanoldimethacrylate, tricyclodecanedimethanol dimethacrylate, hydrogenatedbisphenol A dimethacrylate, and bisphenol A 2-mol propylene oxide adductdimethacrylate. In addition, trifunctional monomers and tetrafunctionalmonomers and the like can also be used. In terms of water resistance andheat resistance, bifunctional or higher polyfunctionality is preferred,but if the cross-linking density becomes too high, the molded productcan become brittle, meaning considerable caution is required. Of thesecompounds, compounds with an ester number of no more than 400 arepreferred in terms of resistance to water absorption and waterresistance. Furthermore, other monomers can also be added for thepurpose of improving various other performance factors, provided theiraddition does not impair the low water absorption or hydrolysisresistance and the like.

The blend ratio between the aforementioned unsaturated resin (A) and theethylenically unsaturated monomer (B) varies depending on thecross-linked structure and properties required of the cured productformed from the unsaturated resin (A) and the ethylenically unsaturatedmonomer (B), but in terms of achieving a favorable balance between themoldability and hot water resistance of the molding material, a weightratio (A)/(B) that falls within a range from 90/10 to 40/60 ispreferred. Ratios from 80/20 to 50/50 are even more desirable. Providedthe ratio (A)/(B) falls within the above range, the moldability of themolding material of the present invention is suitable, and a curedproduct and molded product with superior performance in terms ofmechanical strength and hot water resistance and the like can beobtained.

There are no particular restrictions on the radical polymerizationinitiator (C) used in the present invention, provided it is a compoundcapable of initiating the copolymerization between the aforementionedunsaturated resin (A) and ethylenically unsaturated monomer (B) toeffect curing. Suitable examples include one or more materials selectedfrom amongst thermal polymerization initiators, ultravioletpolymerization initiators, and electron beam polymerization initiatorsand the like. The quantity used of the radical polymerization initiator(C) is preferably within a range from 0.1 to 10 parts by weight, andeven more preferably from 1 to 5 parts by weight, per 100 parts byweight of the mixture of the unsaturated resin (A) and the ethylenicallyunsaturated monomer (B).

Examples of suitable thermal polymerization initiators include organicperoxides such as diacyl peroxide-based compounds, peroxyester-basedcompounds, hydroperoxide-based compounds, ketone peroxide-basedcompounds, alkyl perester-based compounds, and percarbonate-basedcompounds, and of these, the compound that is most suited to the moldingconditions can be selected.

Examples of suitable ultraviolet polymerization initiators includephotosensitizing materials such as acylphosphine oxide-based compounds,benzoin ether-based compounds, benzophenone-based compounds,acetophenone-based compounds, and thioxanthone-based compounds. Ofthese, the compound that is most suited to the molding conditions can beselected and used. Furthermore, examples of suitable electron beampolymerization initiators include halogenated alkylbenzenes anddisulfide-based compounds.

In order to accelerate the curing, a radical polymerization accelerator,that is a curing accelerator, can also be used in combination with theradical polymerization initiator (C). Examples of suitable curingaccelerators include metal salts such as cobalt naphthenate and cobaltoctenoate, and tertiary amines such as N,N-dimethylaniline,N,N-di(hydroxyethyl)para-toluidine, and dimethylacetoacetamide, andthese can be selected and used as required.

Examples of the reinforcing material and/or filler (D) used in thepresent invention include both conductive materials and non-conductivematerials, and an appropriate material may be selected and used inaccordance with the intended application.

Examples of conductive materials used in the present invention includecarbon materials, metals, metal compounds, and conductive polymerpowders, and of these, from the viewpoints of durability and corrosionresistance, carbon-based materials are preferred. Examples of suitablecarbon-based materials include artificial graphite, natural graphite,glass-like carbon, carbon black, acetylene black, ketchen black, andexpanded graphite produced by chemical treatment of graphite. Fibrouscarbon fiber can also be used. In the case of the production of a fuelcell separator, artificial graphite is preferred. The calcinationtemperature of the graphite is typically 2,500° C. or higher, andpreferably 2,700° C. or higher, and even more preferably 2,900° C. orhigher, the average particle size is typically within a range from 1 to500 μm, and preferably from 50 to 350 μm, and the aspect ratio ispreferably no more than 3.5.

Of the above materials, examples of fibrous carbon materials includepitch-based, PAN-based, and rayon-based carbon fiber, which differ inaccordance with the raw material fiber. There are no particularrestrictions on the length or shape of the carbon fibers, although inorder to achieve a bulk molding compound (hereafter referred to as BMC),and considering the mixing characteristics with the resin, the fiberlength is typically no longer than 25 mm, and preferably within a rangefrom 1 μm to 10 mm. Specific examples of carbon fibers of this type oflength include filament fibers, chopped strands, milled fibers, andcarbon nanotubes.

Examples of the metals and metal compounds mentioned above includealuminum, zinc, iron, copper, nickel, silver, gold, stainless steel,palladium, and titanium, as well as the borides of these metals,zirconium boride, hafnium boride, tin-antimony oxide, indium-tin oxide,indium-zinc oxide, indium oxide, and zinc-aluminum oxide. Suitable formsfor these metals and metal compound include particles, fibers, foils, oramorphous forms.

Examples of suitable non-conductive materials include calcium carbonate,magnesium carbonate, mica, talc, kaolin, clay, celite, asbestos,perlite, barite, silica, quartz sand, silicon carbide, boron nitride,dolomite, hollow balloons, alumina, glass powder, glass fiber, aluminumhydroxide, calcite, zirconium oxide, antimony trioxide, titanium oxide,molybdenum dioxide, and aramid fiber.

These materials can be selected appropriately with due consideration tofactors such as workability, and the strength, external appearance, andrequired performance characteristics of the molded product. Typically,calcium carbonate, aluminum hydroxide, silica, talc, alumina, glassfiber, carbon fiber, and aramid fiber are the most commonly used.Suitable fillers also include the materials generated by subjecting thefillers above to surface treatment.

The quantity used of the reinforcing material and/or filler (D) istypically within a range from 1 to 90% by mass of the resin compositionmade up of the aforementioned components (A), (B), (C), and (D).Although dependent on the target application and the requiredperformance characteristics, quantities within a range from 10 to 80% bymass are usually preferred. In the case of the production of a highlyconductive fuel cell separator, a conductive carbon-based material in aquantity within a range from 60 to 85% by mass is preferred as thecomponent (D). If the quantity is less than this range, the conductivityis insufficient, whereas if the quantity is too large, the strength andwater resistance of the molded product tend to decrease unfavorably.

A curable resin composition of the present invention, when used as aradical curing molding material, preferably also contains a thickener(E) in order to improve the handling characteristics of the moldingmaterial described above, and reduce the occurrence of molding defectsupon compression molding.

The thickener (E) may be any organic or inorganic compound that exhibitsa thickening effect. These compounds can be selected and used inaccordance with the intended application.

Examples of suitable organic compounds that can be used in the presentinvention include polyisocyanate compounds, polycarbodiimide compounds,and metal alkoxy compounds. Of these, polyisocyanate compounds arepreferred as they are able to cause thickening through reaction with thehydroxyl groups of the aforementioned unsaturated resin (A) under mildconditions between room temperature and approximately 50° C. Inaddition, acrylic resin-based fine particles are also desirable as theyallow thickening to be achieved easily by heating. Examples ofcommercially available acrylic resin-based fine particles include thepolymethylmethacrylate resin-based product F303 (manufactured by ZeonCorporation).

Examples of suitable inorganic compounds include metal oxides such asfinely powdered silica and magnesium oxide. In those cases wherethickening is conducted using magnesium oxide, the curable moldingmaterial preferably includes a polymer compound that contains acidgroups. Polymers such as copolymers of styrene and (meth)acrylic acidare preferred in terms of the water resistance.

The quantity used of the above thickener (E) varies depending on thecompound used. For example, in those cases where a polyisocyanatecompound is used as the thickener, the use of a quantity ofpolyisocyanate that results in a OH/NCO ratio of 1/0.8 to 1/1.2 relativeto the hydroxyl groups of the unsaturated resin (A) is preferred interms of the hot water resistance. Furthermore, by controlling thisquantity, the moldability of the molding material and the properties ofthe molded product can be controlled.

Specific examples of the above polyisocyanate compound include1,6-hexamethylene diisocyanate, trimethylhexamethylene diisocyanate,4,4′-diphenylmethane diisocyanate, tolylene diisocyanate, xylylenediisocyanate, naphthalene diisocyanate, 1,4-cyclohexane diisocyanate,4,4′-dicyclohexylmethane diisocyanate, isophorone diisocyanate,hydrogenated xylylene diisocyanate, and norbornene diisocyanate.Furthermore, the isocyanurate compounds obtained by isocyanuration ofeach of the above isocyanate compounds can also be used. These compoundscan be used either alone, or in combinations of two or more differentcompounds.

In those cases where acrylic resin-based fine particles are used as thethickener (E), the quantity used is preferably within a range from 10 to50 parts by weight per 100 parts by weight of the mixture of theaforementioned unsaturated resin (A) and ethylenically unsaturatedmonomer (B). In those cases where a metal oxide is used as thethickener, the optimum quantity is determined in accordance with thenature and molecular weight of the compound that contains the acidgroups.

Where required, the curable resin composition of the present inventionmay also include low profile additives, polymerization inhibitors,internal mold release agents, compatibilizing-agent, as well as otheradditives and colorants.

Examples of other additives that can be used include silane-based ortitanate-based coupling agents, flame retardants, ultravioletstabilizers, antioxidants, antistatic agents, hydrophilicity impartingagents, antibacterial agents, water repellents, antifoaming agents, andair blocking agents.

A curable resin composition of the present invention can be used in theproduction of molded products, for example as a sheet molding compound(hereafter referred to as SMC) or a bulk molding compound (hereafterreferred to as BMC) for use as a press molding material, injectionmolding material, hand lay-up molding material, cast molding material,draw molding material, or lining material.

The molded product can be obtained from a molding material that uses anaforementioned curable resin composition, using any of the variousmolding methods.

Examples of suitable molding methods include hand lay-up molding,compression molding, transfer molding, injection molding, draw molding,and rotational molding. Factors such as the shape of the molded productare selected appropriately in accordance with the intended application.

Examples of suitable molded products include household equipment such asbathtubs, kitchen counters, bathroom vanities, and imitation marble,civil engineering and construction materials such as drawn materials andpolymer concrete, industrial members such as the blades for wind powergenerators, vehicle components such as lamp reflectors and carbon fibercomposites for automobiles, as well as electrical equipment componentsand electronic components such as motor sealants, diode sealants,breaker boxes, electrical substrates, and fuel cell separators.

In a method of producing an aforementioned molding material, theunsaturated resin (A), the ethylenically unsaturated monomer (B), theradical polymerization initiator (C), and where required the reinforcingmaterial and/or filler (D) are combined, either in a single batch or insteps, and are then mixed together using a mixing device. The mixing canbe conducted using a mixing device such as a kneader, stirrer, or mixeror the like. The mixing may be conducted either at normal pressures, orunder reduced pressure. Furthermore, the temperature during mixing ispreferably within a range from room temperature to 60° C.

In order to improve the moldability and the handling properties of themixture, the mixture can be converted to a sheet, block, or particles.

In those cases where a thickening step is required for the moldingmaterial, the mixture may be held at a temperature within a range fromroom temperature to 80° C. following mixing, to allow the thickening toproceed. The time required for this step varies depending on factorssuch as the composition of the resin, the kind and quantity of anythickener used, and the temperature conditions, but is typically withina range from 1 to 100 hours.

Even in those cases where a polyisocyanate is used as the thickener (E),a molding material of the present invention retains favorablemoldability and handling properties over an extended period. This is aneffect of having tightly controlled the hydroxyl number, ester number,the sum thereof, and the double bond equivalent weight of theunsaturated resin (A).

Particularly in those cases where a fuel cell separator is produced fromthe molding material, a molding die with a channel that corresponds withthe shape of the separator can be used, and molding can be conductedusing a molding method such as compression molding or injection molding.In such cases, the molding temperature is preferably within a range fromapproximately 100 to 200° C. This temperature is preferably matched tothe optimum temperature band for the thermal polymerization initiatorthat has been used. In terms of productivity, the temperature ispreferably within a range from 140 to 190° C. The molding pressure canbe adjusted to the most suitable pressure in accordance with factorssuch as the molding die used, the shape of the molded product, and theintended application for the product.

This pressure is typically within a range from 5 to 20 MPa. If required,post-curing can be conducted in a heated atmosphere following themolding, to promote further curing or correction.

The heat resistance of the molded product can be evaluated by measuringthe heat distortion temperature in accordance with the method prescribedin JIS-K-7207 (the edgewise method of ISO-75). The heat distortiontemperature of the molded product is the value determined undermeasurement conditions that include a load of 181.3 N/cm², and ispreferably at least 150° C., and even more preferably 200° C. or higher.Particularly in those cases where the molded product is used as a fuelcell separator, a high heat resistance is preferred as it reduces thepossibility of thermal distortion after mounting.

Using conventional resin molding methods, the above molding material canbe molded with precise channels that can act as gas channels, withoutrequiring any cutting processes or the like, and consequently, themolding material is ideal for the production of precision moldedcomponents such as fuel cell separators. Furthermore, molding materialsof the present invention are also useful as putty, sealing materials,adhesives, and dental materials.

A fuel cell separator obtained using a curable resin composition of thepresent invention is preferably used within a fuel cell for which theoperating temperature is no higher than 200° C. This type of fuel cellseparator can be used as the separator in a variety of different fuelcells, including hydrazine fuel cells, direct methanol fuel cells,alkali fuel cells, solid polymer fuel cells, and phosphate fuel cells.Of these, the separator is particularly suited to solid polymer fuelcells.

EXAMPLES

As follows is a description of specifics of the present invention, basedon a series of examples and comparative examples. In the followingdescription, unless stated otherwise, the units “parts” and “%” allrefer to mass-referenced values.

Synthesis Example 1 Production of an Unsaturated Resin (A-1)

A 1 L flask fitted with a thermometer, a nitrogen and air inlet, and astirrer was charged with 470 g of an epoxy resin [product name: Epiclon1055, manufactured by Dainippon Ink and Chemicals, Incorporated, abisphenol A epoxy resin with an epoxy equivalent weight of 470], 154 gof (meth)acrylic anhydride [product name: MAAH, manufactured by RohmLtd.], and 0.2 g of t-butylhydroquinone, and the temperature of themixture was then raised to 90° C. under a stream of a mixed gascontaining a 1:1 ratio of nitrogen and air. To this mixture was added1.2 g of tris-dimethylaminophenol, and when the temperature was thenraised to 110° C. and reaction was conducted for 8 hours, the acidnumber fell below 3, and so the reaction was halted. Following coolingto a temperature of approximately 80° C., the product was removed fromthe reaction vessel, thus yielding the targeted unsaturated resin. Thisresin is referred to below as the resin A-1. The resin A-1 had ahydroxyl number of 82, an ester number of 178, a double bond equivalentweight of 312, a resin viscosity (in a solution containing 20% of astyrene monomer diluent) of 11,000 mPa·s, an aromatic ring structuralunit content of 51%, and a number average molecular weight of 2,100.

Synthesis Example 2 Production of an Unsaturated Resin (A-2)

A similar 1 L four neck flask to that used in the synthesis example 1was charged with 552 g of an epoxy resin [product name: NC-3000,manufactured by Nippon Kayaku Co., Ltd., a biphenyl group-containingphenol novolac epoxy resin with an epoxy equivalent weight of 276], 86 gof methacrylic acid, 154 g of (meth)acrylic anhydride [product name:MAAH, manufactured by Rohm Ltd.], and 0.25 g of t-butylhydroquinone, andthe temperature of the mixture was then raised to 90° C. under a streamof a mixed gas containing a 1:1 ratio of nitrogen and air. To thismixture was added 1.0 g of tris-dimethylaminophenol, and when thetemperature was then raised to 110° C. and reaction was conducted for 6hours, the acid number fell below 3, and so the reaction was halted.Following cooling to a temperature of approximately 80° C., the productwas removed from the reaction vessel, thus yielding the targetedunsaturated resin. This resin is referred to below as the resin A-2. Theresin A-2 had a hydroxyl number of 75, an ester number of 212, a doublebond equivalent weight of 263, a resin viscosity (in a solutioncontaining 20% of a styrene monomer diluent) of 5,100 mPa·s, an aromaticring structural unit content of 45%, and a number average molecularweight of 1,400.

Comparative Synthesis Example 1 Production of a Comparative UnsaturatedResin (V-1)

A similar flask to that used in the synthesis example 1 was charged with380 g of an epoxy resin [product name: Epiclon 850, manufactured byDainippon Ink and Chemicals, Incorporated, a bisphenol A epoxy resinwith an epoxy equivalent weight of 190], 169 g of methacrylic acid, and0.16 g of t-butylhydroquinone, and the temperature of the mixture wasthen raised to 90° C. under a stream of a mixed gas containing a 1:1ratio of nitrogen and air. To this mixture was added 1.1 g oftris-dimethylaminophenol, and when the temperature was then raised to110° C. and reaction was conducted for 10 hours, the acid number fellbelow 4, and so the reaction was halted. Following cooling to atemperature of approximately 80° C., the product was removed from thereaction vessel, thus yielding an unsaturated resin. This resin isreferred to below as the unsaturated resin V-1. The resin V-1 had ahydroxyl number of 198, an ester number of 196, a double bond equivalentweight of 283, a resin viscosity (in a solution containing 20% of astyrene monomer diluent) of 1,780 mPa·s, an aromatic ring structuralunit content of 30%, and a number average molecular weight of 810.

Example 1

70 parts of the unsaturated resin A-1 obtained in the synthesis example1, and 30 parts of styrene were placed in a glass bottle, and stirredand mixed while heating at 50° C. Following cooling to room temperature,2 parts of benzoyl peroxide was added, yielding a resin mixed liquid.The hydroxyl number of the overall resin liquid was 57. Using the thusobtained resin mixed liquid, a molding material was prepared.

A glass chopped strand mat was prepared as a filler. A glass mat with aunit weight of 450 g[m² product name: MC450A, manufactured by NittoBoseki Co., Ltd.] was cut into sheets with dimensions of 20×20 (cm), andthree such sheets were prepared.

Using a 30 cm square glass plate as a substrate, a polyethyleneterephthalate sheet (hereafter referred to as a PET sheet) of thickness38 μm that had been silicon release-treated on one surface was fixed tothe top of the substrate. Subsequently, the aforementioned three cutglass mats (weight: 54 g) were placed on top of the PET sheet, and theabove resin mixed liquid (weight: 200 g) was impregnated thoroughly intothe glass mats using a metal roller. Finally, a PET sheet similar tothat described above was placed on top. To prevent liquid leakage, theperiphery of the structure was then wrapped and sealed with tape, thusyielding a molding material. This molding material is referred to assheet 1.

Example 2

With the exception of replacing the unsaturated resin A-1 with theunsaturated resin A-2, operations were conducted in the same manner asthe example 1, yielding a resin mixed liquid. The hydroxyl number of theoverall resin liquid was 52. A molding material was then prepared in thesame manner as the example 1. This molding material is referred to assheet 2.

Comparative Example 1

With the exception of replacing the unsaturated resin A-1 with V-1,operations were conducted in the same manner as the example 1, yieldinga resin mixed liquid. The hydroxyl number of the overall resin liquidwas 138. A molding material was then prepared in the same manner as theexample 1. This molding material is referred to as sheet 3.

[Evaluation Tests]

The sheet 1, sheet 2, and sheet 3, obtained in the examples 1 and 2, andthe comparative example 1 respectively, were each sandwiched between twoaluminum flat plates of thickness 3 mm, and then allowed to stand for 1hour in a thermostatic chamber at 70° C. The temperature was then raisedfrom 70° C. to 150° C. over a period of approximately 1 hour, and eachsheet was held at this raised temperature for a further 2 hours, beforebeing cooled to room temperature. An FRP molded product of thickness 4.5mm and dimensions of 20 cm×20 cm was obtained.

Each of these FRP molded products was tested for flexural strength,flexural modulus, heat distortion temperature, and boiling waterabsorption, using the conditions outlined below. The results are shownin Table 1.

Flexural strength and flexural modulus: A strip of dimensions 2.5×10(cm) was cut from each of the FRP molded products obtained in the aboveexamples and the comparative example, and using this strip as a testspecimen, a flexural test was conducted at room temperature, inaccordance with JIS-K6911.

Heat distortion temperature: A strip of dimensions 1.27×12 (cm) was cutfrom each of the FRP molded products obtained in the above examples andthe comparative example, and using this strip as a test specimen, a testwas conducted in accordance with JIS-K7191. The test conditions involvedusing an edgewise method with a load of 1.8 MPa.

Boiling water absorption: A sample of dimensions 5×5 (cm) was cut fromeach of the FRP molded products obtained in the above examples and thecomparative example, and using this sample as a test specimen, thespecimen was immersed in ion exchange water at 100° C., and the rate ofincrease in the weight of the sample, relative to the weight prior toimmersion, was measured after 1 hour, after 24 hours, after 100 hours,and after 400 hours. TABLE 1 Comparative Examples example Item 1 2 1Blend Unsaturated A-1 A-2 V-1 quantity resin (A) 70 70 70 (parts)Hydroxyl number 82 75 198 Ester number 178 212 196 Double bond 312 263283 equivalent weight Monomer (B) 30 30 30 styrene Polymerization 0.330.33 0.33 initiator (C) 50% benzoyl peroxide Reinforcing 21 21 21material, filler (D) Glass mat Molded Flexural 120 115 116 productstrength (MPa) performance Flexural 6600 6500 6800 modulus (MPa) Heatdistortion >300 >300 >300 temperature (° C.) Boiling water absorption(%) after 1 hour 0.16 0.12 0.28 after 24 hours 0.62 0.5 1.1 after 100hours 0.82 0.71 1.5 after 400 hours 0.91 0.83 1.8

As is evident from the results shown in Table 1, in the examples 1 and2, the low boiling water absorption values indicate that a high qualitymolded product with excellent resistance to water absorption has beenobtained.

Next, synthesis examples are presented for unsaturated resins (A) thatcan be used for household equipment members, together with examples ofpreparing molding materials, evaluation results for these moldingmaterials, as well as synthesis examples for comparative unsaturatedresins, examples of preparing molding materials using these comparativeunsaturated resins, and evaluation results for these molding materials.The measurement methods and evaluation criteria used within theseexamples are described below.

[Evaluation of External Appearance of Molded Products]

Using the plate-shaped products obtained in each of the above examplesas test specimens, these test specimens were inspected visually in termsof filling characteristics, warping, cracking, blistering, and internalstate. For the filling characteristics, samples in which filling hadoccurred evenly out to the edges were evaluated as “good”, whereassamples in which filling was incomplete, or in which the thickness wasnon-uniform were evaluated as “poor”. Warping, cracking, and blisteringwere reported as either “no” in those cases where absolutely nooccurrences were observed on the test specimen, or “yes” if even a minoroccurrence was detected. The internal state was evaluated by visuallyinspecting a cross section of the test specimen, and was evaluated aseither “good” if the cross section was dense, or “many voids” if manyhollow voids were present.

[Measurement of Flexural Strength of Molded Products]

The plate-shaped products obtained in the examples described below werecut to the prescribed size to prepare test specimens, and the flexuralstrength was then measured in accordance with JIS K-6911. The atmosphereduring measurement was set at 25° C. The test specimens were cut to awidth of 2.5 cm and a length of 7 cm.

[Measurement of Heat Distortion Temperature of Molded Products]

The plate-shaped products obtained in the examples described below werecut to the prescribed size to prepare test specimens, and the heatdistortion temperature was then measured in accordance with the A methodof JIS K-7207. The load during measurement was 181.3 N/cm².

[Evaluation of Hot Water Resistance of Molded Products (StrengthRetention Test Method)]

The plate-shaped products obtained in the examples described below werecut to the prescribed size to prepare test specimens. A 1.5 L pressurevessel (pressure vessel manufactured from SUS316L, product name:TEM-D1000, manufactured by Taiatsu Techno Corporation) was charged with30 test specimens and 1 L of ion exchange water, and the vessel was thensealed. The vessel was then placed in a 50° C. constant temperature oilbath, and the temperature of the oil bath was raised so that theinternal temperature reached 110° C. in approximately 2 hours.Subsequently, the specimens were left immersed in the ion exchange waterfor 200 hours while the internal temperature was maintained at 110±1° C.Following completion of this predetermined time, the vessel was removedfrom the oil bath, and allowed to cool gradually for approximately 12hours at room temperature, and following release of the pressure, thetest specimens were removed. The recovered test specimens were left tostand for approximately 48 hours at room temperature, and the flexuralstrength was then measured in accordance with JIS K-6911. The strengthretention rate (%) relative to the strength prior to immersion wascalculated, and evaluated using the four stages of criteria listedbelow. The atmosphere during measurement was set to 25° C.

1: The retention rate (%) relative to the strength prior to immersionwas at least 0% but less than 40%.

2: The retention rate (%) relative to the strength prior to immersionwas at least 40% but less than 60%.

3: The retention rate (%) relative to the strength prior to immersionwas at least 60% but less than 80%.

4: The retention rate (%) relative to the strength prior to immersionwas at least 80% but no more than 110%.

[Evaluation of Weight Reduction Ratio for Molded Products]

Test specimens of the same shape as those used for the flexural testwere immersed in hot water under the same conditions as those describedabove, and the test specimens were then allowed to stand for 48 hours atroom temperature. The test specimens were then force dried for 48 hoursat 90° C., and then allowed to stand for a further 1 hour at roomtemperature, before the weight was measured. The weight reduction ratiorelative to the initial weight was calculated.

In terms of molded product performance, products with low weightreduction ratios are preferred.

[Evaluation of External Appearance of Molded Products following HotWater Resistance Testing]

Test specimens of the same shape as those used for the flexural testwere immersed in hot water under the same conditions as those describedabove, and the test specimens were then allowed to stand for 48 hours atroom temperature, and then evaluated visually in terms of their externalappearance.

In terms of gloss, test specimens with gloss irregularities wereevaluated as “poor”, while those with no such irregularities wereevaluated as “good”. In terms of blistering, test specimens withblisters were recorded using “yes”, while those with no blistering wererecorded using “no”. Molded products with no gloss irregularities and noblistering are preferred.

Synthesis Example 3 Production of an Unsaturated Resin (A-3)

A 1 L four neck flask fitted with a nitrogen and air inlet was chargedwith 296 g of an epoxy resin [product name: Epiclon 850, manufactured byDainippon Ink and Chemicals, Incorporated, a bisphenol A epoxy resinwith an epoxy equivalent weight of 190], and 206 g of another epoxyresin [product name: Epiclon 1050, manufactured by Dainippon Ink andChemicals, Incorporated, a bisphenol A epoxy resin with an epoxyequivalent weight of 470], and the mixture was stirred while thetemperature was raised to 90° C. The epoxy equivalent weight of themixture at this point was 251. Subsequently, 31 g of methacrylic acid,0.3 g of t-butylhydroquinone, and 0.8 g of tris-dimethylaminophenol wereadded at 90° C., and the temperature of the mixture was then raised to105° C. under a stream of a mixed gas containing a 1:1 ratio of nitrogenand air. Following raising of the temperature to 105° C. and subsequentreaction for 1 hour, the acid number had fallen below 5, and so thetemperature was cooled to approximately 100° C., and 246 g of(meth)acrylic anhydride [product name: MAAH, manufactured by Rohm Ltd.]was added dropwise with due care given to heat generation. Subsequently,0.8 g of tris-dimethylaminophenol was added, and the temperature wasraised to 110° C. When the mixture was reacted for 5 hours at 110° C.,the acid number fell below 5, and so the reaction was halted. Followingcooling to a temperature of approximately 80° C., the product wasremoved from the reaction vessel, thus yielding an unsaturated resin.This resin is referred to below as the unsaturated resin A-3. Theunsaturated resin A-3 had a hydroxyl number of 61, an ester number of251, a double bond equivalent weight of 238, a resin viscosity (in asolution containing 20% of a styrene monomer diluent) of 1,380 mPa·s, anaromatic ring structural unit content of 30%, and a number averagemolecular weight of 1,020.

Synthesis Example 4 Production of an Unsaturated Resin (A-4)

A similar flask to that used in the synthesis example 1 was charged with548 g of an epoxy resin [product name: NC-3000, manufactured by NipponKayaku Co., Ltd., a biphenyl group-containing phenol novolac epoxy resinwith an epoxy equivalent weight of 274], and the resin was stirred whilethe temperature was raised to 90° C. Subsequently, 55 g of methacrylicacid, 0.4 g of t-butylhydroquinone, and 0.8 g oftris-dimethylaminophenol were added at 90° C., and the temperature ofthe mixture was then raised to 105° C. under a stream of a mixed gascontaining a 1:1 ratio of nitrogen and air. Following raising of thetemperature to 105° C. and subsequent reaction for 2 hours, the acidnumber had fallen below 5, and so the temperature was cooled toapproximately 100° C., and 203 g of (meth)acrylic anhydride [productname: MAAH, manufactured by Rohm Ltd.] was added dropwise with due caregiven to heat generation. Subsequently, 0.8 g oftris-dimethylaminophenol was added, and the temperature was raised to110° C. When the mixture was reacted for 6 hours at 110° C., the acidnumber fell below 5, and so the reaction was halted. Following coolingto a temperature of approximately 80° C., the product was removed fromthe reaction vessel, thus yielding an unsaturated resin. This resin isreferred to below as the unsaturated resin A-4. The unsaturated resinA-4 had a hydroxyl number of 48, an ester number of 225, a double bondequivalent weight of 245, a resin viscosity (in a solution containing20% of a styrene monomer diluent) of 4,300 mPa·s, an aromatic ringstructural unit content of 44%, and a number average molecular weight of1,300.

Comparative Synthesis Example 2 Production of a Comparative UnsaturatedResin (V-2)

A similar flask to that used in the synthesis example 1 was charged with380 g of an epoxy resin [product name: Epiclon 850, manufactured byDainippon Ink and Chemicals, Incorporated, a bisphenol A epoxy resinwith an epoxy equivalent weight of 190], and the temperature was raisedto 80° C. under a stream of a mixed gas containing a 1:1 ratio ofnitrogen and air. Subsequently, 4 g of triphenylphosphine, 17.2 g ofmethacrylic acid, and 0.33 g of t-butylhydroquinone were added, and then277.2 g of (meth)acrylic anhydride [product name: MAAH, manufactured byRohm Ltd.] was added dropwise with due care given to heat generation.Following completion of the dropwise addition, the temperature wasraised to 90° C. When the mixture was reacted for 5 hours at 90° C., theacid number fell below 3, and so the reaction was halted. Followingcooling to a temperature of approximately 80° C., the product wasremoved from the reaction vessel, thus yielding an unsaturated resin.This resin is referred to below as the unsaturated resin V-2. The resinV-2 had a hydroxyl number of 17, an ester number of 314, a double bondequivalent weight of 178, a resin viscosity (in a solution containing20% of a styrene monomer diluent) of 350 mPa·s, an aromatic ringstructural unit content of 24%, and a number average molecular weight of830.

A list of the components used in the following examples, with theexception of the resins obtained in the above synthesis examples 1through 4, and the comparative synthesis examples 1 and 2, is providedbelow.

Styrene monomer: hereafter referred to as monomer B-1.

Tertiary butylperoxyisopropyl carbonate [product name: BIC-75,manufactured by Kayaku Akzo Corporation]: referred to as initiator C-1.

p-benzoquinone [product name: p-BQ, manufactured by Eastman ChemicalCompany]: hereafter referred to as inhibitor-1.

Zinc stearate: hereafter referred to as mold release agent-1.

Calcium carbonate [product name: MM-100D, manufactured by Maruo CalciumCo., Ltd., average particle size: 3 μm: referred to as filler D-1.

Glass chopped strands [product name: CS6PA-473S, manufactured by NittoBoseki Co., Ltd., fiber length: 6 mm]: hereafter referred to asreinforcing material D-2.

Examples 3 and 4 Preparation of Molding Materials and Molded Products

Using the unsaturated resins A-3 and A-4 produced in the synthesisexamples 3 and 4, and the other blend components described above, thecomponents shown in the Table 2 were blended together in the quantitiesshown, together with 0.002 parts of the inhibitor-1 and 1 part of themold release agent-1, and each of the resulting mixtures was mixedthoroughly at room temperature using a kneader, thus yielding a moldingmaterial. This molding material was packaged tightly inside a styreneimpermeable multilayer film, and was then stored at room temperature.Two days after preparation, the molding material was removed from themultilayer film, filled a flat sheet molding die, and molded with acompression molding device, under conditions including a pressure of 180kgf/cm² (gauge pressure), an upper mold temperature of 150° C., a lowermold temperature of 145° C., and a molding time of 10 minutes, therebyproducing a plate-shaped product with a width of 30 cm, a length of 30cm, and a thickness of 2.8 mm. This plate-shaped product was evaluatedfor flexural strength, heat distortion temperature, and hot waterresistance. The results of these evaluations are shown in Table 3.

Comparative Examples 2 and 3

With the exception of replacing the unsaturated resins A-3 and A-4 usedin the examples 3 and 4 with the unsaturated resins V-1 and V-2 producedin the comparative synthesis examples 1 and 2, molding materials andmolded products of the comparative examples 2 and 3 were produced in thesame manner as the examples. The blend quantities used are shown inTable 2. The results of the evaluations are shown in Table 3. TABLE 2Examples Comparative examples Item 3 4 2 3 Blend Unsaturated resin A-3A-4 V-1 V-2 quantity (A) 15.5 15.5 15.5 15.5 (parts) Hydroxyl number 6148 198 17 Ester number 251 225 196 314 Double bond 238 245 283 178equivalent weight Monomer (B) Monomer B-1 6.5 6.5 6.5 6.5 Initiator (C)Initiator C-1 0.33 0.33 0.33 0.33 Reinforcing agent, filler (D) FillerD-1 66.5 66.5 66.5 66.5 Reinforcing agent 10.2 10.2 10.2 10.2 D-2

TABLE 3 Examples Comparative examples Item 3 4 2 3 Flowability duringmolding Plate-shaped product 3 3 3 3 Molded product external appearanceFilling characteristics Good Good Good Poor Warping No No No No CrackingNo No No No Internal state Good Good Good Good Flexural strength (MPa)83 85 88 78 Heat distortion temperature >300 >300 >300 >300 (° C.) Howwater resistance (110° C. × 200 hours) Strength retention rate 4 4 4 3Weight reduction ratio (%) 0.28 0.25 0.55 0.59 External appearance GlossGood Good Poor Good Blistering No No No Yes

As is evident from the results shown in Table 3, the materials of theexamples 3 and 4 exhibit excellent moldability, enable the production ofhigh quality molded products, and also exhibit high levels of heatresistance and hot water resistance. Accordingly, materials that areideal as household equipment members and electrical members can beprovided. In contrast, it is also evident from the results shown inTable 3 that although the materials of the comparative examples 2 and 3exhibit favorable moldability, the resulting molded products eithersuffered from low heat resistance, poor hot water resistance, orexternal appearance problems after the hot water test. Furthermore, theweight reduction ratios also tended to be higher.

Next, synthesis examples are presented for unsaturated resins (A) thatcan be used as fuel cell separators, together with examples of preparingmolding materials, and evaluation results for these molding materials.

The measurement methods and evaluation criteria used within theseexamples are the same as those described above, although the evaluationmethods for additional test items are described below.

[Evaluation of Handling Properties of Conductive Molding Materials]

When each of the conductive molding materials obtained in the followingexamples was removed from the multilayer film used for storage of thematerial, the releasability of the material from the film, and the levelof stickiness of the resin surface were evaluated visually. The resultswere classified into two levels.

Poor: the releasability from the film was poor, and the stickiness ofthe resin composition surface was considerable.

Good: the releasability from the film was good, and the resincomposition surface was not sticky.

[Evaluation of Flowability During Molding for Conductive MoldingMaterials]

Each of the conductive molding materials obtained in the followingexamples was molded using a 50t transfer molding apparatus, underconditions including a pressure of 150 kgf/cm² (gauge pressure), apiston speed of 1 mm/second, and a temperature of 150° C. Thecross-sectional dimensions of the molded product were 7×2 (mm). Thespiral flow length of the cured product at this point was measured, andthe result was classified into one of the following four levels.

1: at least 0 cm, but less than 20 cm.

2: at least 20 cm, but less than 40 cm.

3: at least 40 cm, but less than 80 cm.

4: at least 80 cm.

In order to achieve favorable mold filling characteristics and obtain adense molded product with no voids, a result of 3: at least 40 cm, butless than 80 cm is preferred for the above evaluation. An evaluationresult of 1: less than 20 cm indicates poor filling characteristics,whereas an evaluation result of 4: at least 80 cm may indicate it isdifficult to obtain a dense molded product.

[Evaluation of External Appearance of Molded Products]

With the exception of using the fuel cell separators obtained in theexamples described below as the test specimens, evaluation was conductedin the same manner as the tests described above.

[Measurement of Conductivity of the Molded Products]

Test specimens with a width of 1 cm, thickness of 3 mm, and length of 10cm were cut from the plate-shaped products obtained in the followingexamples, and the volumetric resistivity of each test specimen wasmeasured in accordance with JIS C-2525.

[Measurement of Flexural Strength of Molded Products], [Measurement ofHeat Distortion Temperature of Molded Products], and [Evaluation of HotWater Resistance of Molded Products (Strength retention test method)]were each conducted in the same manner as described above. However, inthe evaluation of the hot water resistance, the previous test conditionsof 110° C.×200 hours were altered to 150° C.×240 hours.

Synthesis Example 5 Production of an Unsaturated Resin (A-5)

A similar flask to that used in the synthesis example 1 was charged with520 g of an epoxy resin [product name: Epiclon HP-7200, manufactured byDainippon Ink and Chemicals, Incorporated, a dicyclopentadiene phenolnovolac epoxy resin with an epoxy equivalent weight of 260], and theresin was stirred while the temperature was raised to 90° C.Subsequently, 86 g of methacrylic acid, 0.4 g of t-butylhydroquinone,and 0.8 g of tris-dimethylaminophenol were added at 90° C., and thetemperature of the mixture was then raised to 105° C. under a stream ofa mixed gas containing a 1:1 ratio of nitrogen and air. Followingraising of the temperature to 105° C. and subsequent reaction for 2hours, the acid number had fallen below 5, and so the temperature wascooled to approximately 100° C., and 142 g of (meth)acrylic anhydride[product name: MAAH, manufactured by Roehm Ltd.] was added dropwise withdue care given to heat generation. Subsequently, 0.7 g oftris-dimethylaminophenol was added, and the temperature was raised to110° C. When the mixture was reacted for 6 hours at 110° C., the acidnumber fell below 5, and so the reaction was halted. Following coolingto a temperature of approximately 80° C., the product was removed fromthe reaction vessel, thus yielding an unsaturated resin (A). This resinis referred to below as the unsaturated resin A-5. The unsaturated resinA-5 had a hydroxyl number of 80, an ester number of 215, a double bondequivalent weight of 258, a resin viscosity (in a solution containing20% of a styrene monomer diluent) of 5,200 mPa·s, an aromatic andaliphatic ring structural unit content of 40%, and a number averagemolecular weight of 900.

Synthesis Example 6 Production of an Unsaturated Resin (A-6)

A similar flask to that used in the synthesis example 1 was charged with548 g of an epoxy resin [product name: NC-3000, manufactured by NipponKayaku Co., Ltd., a biphenyl group-containing phenol novolac epoxy resinwith an epoxy equivalent weight of 274], and the resin was stirred whilethe temperature was raised to 90° C. Subsequently, 79 g of methacrylicacid, 0.4 g of t-butylhydroquinone, and 0.8 g oftris-dimethylaminophenol were added at 90° C., and the temperature ofthe mixture was then raised to 105° C. under a stream of a mixed gascontaining a 1:1 ratio of nitrogen and air. Following raising of thetemperature to 105° C. and subsequent reaction for 2 hours, the acidnumber had fallen below 5, and so the temperature was cooled toapproximately 100° C., and 160 g of (meth)acrylic anhydride [productname: MAAH, manufactured by Rohm Ltd.] was added dropwise with due caregiven to heat generation. Subsequently, 0.7 g oftris-dimethylaminophenol was added, and the temperature was raised to110° C. When the mixture was reacted for 6 hours at 110° C., the acidnumber fell below 5, and so the reaction was halted. Following coolingto a temperature of approximately 80° C., the product was removed fromthe reaction vessel, thus yielding an unsaturated resin (A). This resinis referred to below as the unsaturated resin A-6. The unsaturated resinA-6 had a hydroxyl number of 71, an ester number of 211, a double bondequivalent weight of 263, a resin viscosity (in a solution containing20% of a styrene monomer diluent) of 5,000 mPa·s, an aromatic ringstructural unit content of 45%, and a number average molecular weight of1,390.

Synthesis Example 7 Production of an Unsaturated Resin (A-7)

A similar flask to that used in the synthesis example 1 was charged with578 g of an epoxy resin [product name: NC-3000H, manufactured by NipponKayaku Co., Ltd., a biphenyl group-containing phenol novolac epoxy resinwith an epoxy equivalent weight of 289], and the resin was stirred whilethe temperature was raised to 90° C. Subsequently, 48 g of methacrylicacid, 0.4 g of t-butylhydroquinone, and 0.8 g oftris-dimethylaminophenol were added at 90° C., and the temperature ofthe mixture was then raised to 105° C. under a stream of a mixed gascontaining a 1:1 ratio of nitrogen and air. Following raising of thetemperature to 105° C. and subsequent reaction for 1 hour, the acidnumber had fallen below 5, and so the temperature was cooled toapproximately 100° C., and 215 g of (meth)acrylic anhydride [productname: MAAH, manufactured by Rohm Ltd.] was added dropwise with due caregiven to heat generation. Subsequently, 0.8 g oftris-dimethylaminophenol was added, and the temperature was raised to110° C. When the mixture was reacted for 7 hours at 110° C., the acidnumber fell below 5, and so the reaction was halted. Following coolingto a temperature of approximately 80° C., the product was removed fromthe reaction vessel, thus yielding an unsaturated resin (A). This resinis referred to below as the unsaturated resin A-7. The unsaturated resinA-7 had a hydroxyl number of 40, an ester number of 221, a double bondequivalent weight of 250, a resin viscosity (in a solution containing20% of a styrene monomer diluent) of 12,600 mPa·s, an aromatic ringstructural unit content of 46%, and a number average molecular weight of1,770.

Comparative Synthesis Example 3 Production of a Comparative UnsaturatedResin (V-3)

A similar flask to that used in the synthesis example 1 was charged with520 g of an epoxy resin [product name: Epiclon HP-7200, manufactured byDainippon Ink and Chemicals, Incorporated, a dicyclopentadiene phenolnovolac epoxy resin with an epoxy equivalent weight of 260], 168 g ofmethacrylic acid, and 0.29 g of t-butylhydroquinone, and the temperaturewas raised to 90° C. under a stream of a mixed gas containing a 1:1ratio of nitrogen and air. Subsequently, 1.5 g oftris-dimethylaminophenol was added, and when the temperature of themixture was raised to 110° C. and reaction was conducted for 10 hours,the acid number fell below 5, and so the reaction was halted. Followingcooling to a temperature of approximately 80° C., the product wasremoved from the reaction vessel, thus yielding an unsaturated resin.This resin is referred to below as the unsaturated resin V-3. Theunsaturated resin V-3 had a hydroxyl number of 162, an ester number of153, a double bond equivalent weight of 352, a resin viscosity (in asolution containing 20% of a styrene monomer diluent) of 8,600 mPa·s, anaromatic and aliphatic ring structural unit content of 44%, and a numberaverage molecular weight of 870.

A list of the components used in the following examples, with theexception of the resins obtained in the above synthesis examples 5through 7, and the comparative synthesis examples 1 and 3, and the rawmaterials used in the above molding material examples 3 and 4, isprovided below.

Divinylbenzene [product name: DVB-810, manufactured by Nippon SteelChemical Co., Ltd., purity: 81%]: hereafter referred to as monomer B-2.

Modified liquid compound of diphenylmethane diisocyanate [product name:Isonate 143LJ, manufactured by Dow Polyurethane Japan Ltd., NCO: 29%]:hereafter referred to as thickener (polyisocyanate) E-1.

Polystyrene resin [product name: Dicstyrene CR-2500, manufactured byDainippon Ink and Chemicals, Incorporated, molecular weight: 200,000]:hereafter referred to as low profile additive-1.

Compatibilizing-agent [product name: RS-900, manufactured by DainipponInk and Chemicals, Incorporated]: hereafter referred to ascompatibilizing-agent-1.

Perfluoropolyether [product name: Fluorolink D10-H, manufactured bySolvay Solexis Inc., molecular weight: 1,500]: hereafter referred to asmold release agent-2.

Synthetic graphite [product name: K-100, manufactured by Applied CarbonTechnology, Inc., average particle size: 300 μm hereafter referred to asfiller D-3.

Examples 5 to 8 Preparation of Conductive Molding Materials and MoldedProducts

Using the unsaturated resins A-5, A-6, and A-7 produced in the synthesisexamples to 7, and the other blend components such as B-1, B-2, C-1,D-3, and E-1 described above, the components shown in the Table 4 wereblended together in the quantities shown, together with 0.01 parts ofthe inhibitor-1 and 0.2 parts of the mold release agent-2, and each ofthe resulting mixtures was mixed thoroughly at room temperature using akneader, thus yielding a curable resin composition, and a conductivemolding material. This molding material was packaged tightly inside astyrene monomer impermeable multilayer film. Following thickening for 2days at 30° C., the conductive molding material was returned to roomtemperature and stored. Three days after preparation, the moldingmaterial was removed from the aforementioned multilayer film, filled afuel cell separator-shaped molding die and a flat sheet molding die, andmolded with a compression molding device, under conditions including apressure of 150 kgf/cm² (gauge pressure), an upper mold temperature of150° C., a lower mold temperature of 145° C., and a molding time of 10minutes, thereby producing a fuel cell separator with a width of 13 cm,a length of 20 cm, and a thickness of 3 mm, and a plate-shaped product.The handling properties of the resin composition were evaluated. Thefuel cell separator was evaluated for external appearance, and theplate-shaped product was evaluated for conductivity, flexural strength,heat distortion temperature, and hot water resistance. The results ofthese evaluations are shown in Table 6.

Comparative Examples 4 to 6 Preparation of Comparative Molding Materialsand Molded Products

With the exception of replacing the unsaturated resins (A) used in theexamples 5 through 8 with the unsaturated resins V-1 and V-3 prepared inthe comparative synthesis examples 1 and 3, conductive molding materialsand molded products were produced in the same manner as the examples 5to 8. In these cases, the blend quantity of the total resin componentwas adjusted to ensure that the added quantity of the conductive fillerwithin each of the molding materials was the same. The blend quantitiesare shown in Table 5. The results of the evaluations are shown in Table7. TABLE 4 Examples Item 5 6 7 8 Blend Unsaturated resin A-3 A-4 A-4 A-5quantity (A) 13.0 13.2 12.9 13.5 (parts) Hydroxyl number 80 71 71 40Ester number 215 211 211 221 Double bond 258 263 263 250 equivalentweight Monomer (B) Monomer B-2 2.9 2.9 2.9 3.0 Monomer B-1 5.8 5.9 5.75.9 Initiator (C) C-1 0.2 0.2 0.2 0.2 Filler (D) D-3 75 75 75 75Thickener (E) E-1 2.9 2.6 2.4 1.5 Low profile 0 0 0.6 0.6 additive-1Compatibilizing- 0 0 0.1 0.1 agent-1 Polyisocyanate 1.0/1.07 1.0/1.071.0/1.01 1.0/1.07 OH/NCO ratio

TABLE 5 Comparative examples Item 4 5 6 Blend Unsaturated resin (A) V-1V-3 V-3 quantity 11.7 12.1 14.8 (parts) Hydroxyl number 198 162 162Ester number 196 153 153 Double bond equivalent weight 283 352 352Monomer (B) Monomer B-2 2.6 2.7 2.9 Monomer B-1 5.1 5.4 6.9 Initiator(C) Initiator C-1 0.2 0.2 0.2 Filler (D) D-3 75 75 75 Thickener (E) E-15.2 4.4 0 Low profile additive-1 0 0 0 Compatibilizing-agent-1 0 0 0Polyisocyanate 1.0/0.88 1.0/0.88 1.0/0.0 OH/NCO ratio

TABLE 6 Examples Item 5 6 7 8 Handling properties Good Good Good GoodFlowability during molding 3 days after production 3 3 3 3 15 days afterproduction 3 3 3 3 Molded product external appearance Fillingcharacteristics Good Good Good Good Warping No No No No Cracking No NoNo No Internal state Good Good Good Good Conductivity Volumetricresistivity 5 6 6 4 (mΩ · cm) Flexural strength (MPa) 33 36 35 33 Heatdistortion temperature 285 >300 >300 >300 (° C.) How water resistance(150° C. × 240 hours) Strength retention rate 4 4 4 4 Weight reductionratio (%) 0.38 0.35 0.33 0.29

TABLE 7 Comparative examples Item 4 5 6 Handling properties Good GoodPoor Flowability during molding 3 days after production 3 1 4 15 daysafter production 2 1 4 Molded product external appearance Fillingcharacteristics Poor Poor Good Warping Yes Yes No Cracking No Yes NoInternal state Good Good Many voids Conductivity Volumetric resistivity(mΩ · cm) 12 27 4 Flexural strength (MPa) 38 36 30 Heat distortiontemperature (° C.) 235 274 192 How water resistance (150° C. × 240hours) Strength retention rate 2 3 1 Weight reduction ratio (%) 2.2 1.52.8

As is evident from the results shown in Table 6, the materials of theexamples 5 to 8 exhibit excellent moldability, enable the production ofhigh quality molded products, and also exhibit high levels of heatresistance and hot water resistance. Accordingly, materials that areideal as separator materials for fuel cells can be provided. Incontrast, it is also evident from the results shown in Table 7 that thematerials of the comparative examples 4 to 6 exhibit poor moldability,and the resulting molded products suffer significant defects, meaningtheir practical applicability is poor. Furthermore, the hot waterresistance values also tended to be lower. The weight reduction ratiosalso tended to be higher, indicating a larger quantity of elutedmaterial, and making the products unsuitable as separator materials.

INDUSTRIAL APPLICABILITY

A curable resin composition according to the present invention, whenused as a molding material, exhibits excellent flowability duringmolding and excellent handling properties, suffers no moldabilityproblems during molding such as the occurrence of fillinginconsistencies, voids, warping, or cracking, and enables the provisionof a molded product with excellent transferability from the molding die,and superior dimensional precision. Furthermore, a molded productobtained by curing a curable resin composition according to the presentinvention exhibits excellent external appearance, and excellent levelsof water absorption resistance, hot water resistance, and mechanicalstrength, as well as particularly superior durability such as waterresistance. Accordingly, a molded product obtained by curing a curableresin composition of the present invention is extremely useful, not onlyfor household equipment members, but also for electronic and electricalmembers, vehicle members, and fuel cell separators used under severeconditions.

1. A curable resin composition, which is a solid resin at ordinary temperatures produced by reacting at least one of a dicyclopentadiene-based novolac epoxy resin and a biphenyl-based novolac epoxy resin with a (meth)acrylic anhydride, and which comprises an unsaturated resin having a (meth)acryloyl group (A) which has a double bond equivalent weight of 200 to 500, an ester number of 100 to 300, and a hydroxyl number of no more than 130, an ethylenically unsaturated monomer (B), and a radical polymerization initiator (C).
 2. A curable resin composition according to claim 1, wherein a number average molecular weight of said unsaturated resin (A) is from 900 to 5,000.
 3. A curable resin composition according to claim 1, wherein a sum of a hydroxyl number and an ester number of said unsaturated resin (A) is from 120 to
 320. 4. A curable resin composition according to claim 1, wherein a hydroxyl number of said unsaturated resin (A) is from 20 to
 130. 5. A curable resin composition according to claim 1, wherein said unsaturated resin comprises from 20 to 80% by mass of aromatic ring structural units and/or aliphatic alicyclic ring structural units.
 6. (canceled)
 7. A molding material, comprising a curable resin composition according to claim 1, and further comprising a reinforcing agent and/or a filler (D).
 8. A molding material for producing a fuel cell separator, comprising a curable resin composition according to claim 1, and further comprising a conductive carbon-based material and a polyisocyanate compound.
 9. A fuel cell separator produced by molding a molding material according to claim
 7. 